package org.apache.lucene.index;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * Provides access to stored term vector of a document field. The vector
 * consists of the name of the field, an array of the terms tha occur in the
 * field of the {@link org.apache.lucene.document.Document} and a parallel array
 * of frequencies. Thus, getTermFrequencies()[5] corresponds with the frequency
 * of getTerms()[5], assuming there are at least 5 terms in the Document.
 */
public interface TermFreqVector {
	/**
	 * The {@link org.apache.lucene.document.Fieldable} name.
	 * 
	 * @return The name of the field this vector is associated with.
	 * 
	 */
	public String getField();

	/**
	 * @return The number of terms in the term vector.
	 */
	public int size();

	/**
	 * @return An Array of term texts in ascending order.
	 */
	public String[] getTerms();

	/**
	 * Array of term frequencies. Locations of the array correspond one to one
	 * to the terms in the array obtained from <code>getTerms</code> method.
	 * Each location in the array contains the number of times this term occurs
	 * in the document or the document field.
	 */
	public int[] getTermFrequencies();

	/**
	 * Return an index in the term numbers array returned from
	 * <code>getTerms</code> at which the term with the specified
	 * <code>term</code> appears. If this term does not appear in the array,
	 * return -1.
	 */
	public int indexOf(String term);

	/**
	 * Just like <code>indexOf(int)</code> but searches for a number of terms
	 * at the same time. Returns an array that has the same size as the number
	 * of terms searched for, each slot containing the result of searching for
	 * that term number.
	 * 
	 * @param terms
	 *            array containing terms to look for
	 * @param start
	 *            index in the array where the list of terms starts
	 * @param len
	 *            the number of terms in the list
	 */
	public int[] indexesOf(String[] terms, int start, int len);

}
